The Proto-Ribosome: An Ancient Nano-machine for Peptide Bond Formation

The ribosome is a ribozyme whose active site, the peptidyl transferase center (PTC), is situated within a highly conserved universal symmetrical region that connects all ribosomal functional centers involved in amino acid polymerization. The linkage between this elaborate architecture and A-site tRNA position revealed that the A- to P-site passage of the tRNA 3′ terminus during protein synthesis is performed by a rotary motion, synchronized with the overall tRNA/mRNA sideways movement, and guided by the PTC. This rotary motion leads to suitable stereochemistry for peptide bond formation as well as for substrate-mediated catalysis. Analysis of the substrate binding modes to ribosomes led to the hypothesis that the ancient ribosome produced single peptide bonds and non-coded chains, potentially in a similar manner to the modern PTC. Later in evolution, a mechanism, enabling some type of decoding genetic control triggered the emergence of the small ribosomal subunit or part of it. This seems to be the result of the appearance of reaction products that could have evolved after polypeptides capable of enzymatic function were generated sporadically, while an ancient stable RNA fold was converted into an old version of a tRNA molecule. Since in the contemporary ribosome, the symmetry relates only to the backbone fold and nucleotide orientations but not nucleotide sequences, it emphasizes the superiority of functional requirement over sequence conservation, and indicates that the PTC may have evolved by gene fusion or gene duplication.     

An alternative strategy for corn drying (Zea mays) resulted in both energy savings and reduction of fumonisins B1 and B2 contamination

The objectives of this study were to investigate the effect of harvest date on fumonisins contamination and to offer an alternative drying procedure with low energy costs. Corn kernel samples above 13% moisture content were dried with hot air (HA), the technique more usually utilised by farmers and compared with infrared and infrared–hot air (IR–HA) combination techniques. The effect of harvest date on fumonisin contamination was found to be significant while drying had no influence. Due to the fact that the corn remains in the field longer than necessary for economic reasons, energy expenses of the drying techniques were calculated in terms of specific energy consumption for unit of evaporated water. It was found that the energy expenses to reduce the moisture level from 15 to 13% with HA drying were higher than the expenses to reduce the moisture level from 29 to 13% with IR–HA drying combination.     

The influence of the surface finishing on the electrochemical behaviour of austenitic and superaustenitic steels

The influence of surface roughness on the pitting potential and the corrosion potential of the DIN W.Nr. 1.4541 and DIN W.Nr 1.4465 stainless steels were examined using electrochemical techniques. Roughness and electrochemical tests were performed on samples with various surface finishing. Electrochemical studies were conducted in an electrochemical cell where steel electrodes were immersed in 0.1 M NaCl and 0.1 M NaCl + 0.1 M Na₂SO₄ aqueous solutions. We found for both materials when immersed in 0.1 M NaCl aqueous solution lower pitting potential than in 0.1 M NaCl + 0.1 M Na₂SO₄. The results showed that the electrochemical behaviour of the DIN W.Nr. 1.4465 is better than of DIN W.Nr. 1.4541.     

Physically-based models of low-power wireless links using signal power simulation

We propose deriving wireless simulation models from experimental traces of radio signal strength. Because experimental traces have holes due to packet losses, we explore two algorithms for filling the gaps in lossy experimental traces. Using completed traces, we apply the closest-fit pattern matching (CPM) algorithm, originally designed for modeling external interference, to model signal strength.We compare the observed link behavior using our models with that of the experimental packet trace. Our approach results in more accurate packet reception ratios (PRR) than current simulation methods, reducing the absolute error in PRR by up to about 0.3 in the experiments we present. We also find that using CPM for signal strength improves simulation of packet burstiness, reducing the Kantorovich–Wasserstein (KW) distance of conditional packet delivery functions (CPDFs) by a factor of about three for intermediate links. Our model reduces the factor of error in the number of parent changes in the standard TinyOS collection protocol (CTP) by an order of magnitude or more as compared to a real signal power trace in two simple test scenarios. We show that our methods are robust to the sampling frequency of the learning deployment and are thus generally applicable for simulating arbitrary applications without a pre-determined packet transmission frequency.These improvements give low-power wireless network simulators a better capability to capture real-world dynamics and edge conditions that protocol designers typically must wait until deployment to detect.     

Effects of clinical mastitis caused by gram-positive and gram-negative bacteria and other organisms on the probability of conception in New York State Holstein dairy cows

The objective of this study was to estimate the effects of different types of clinical mastitis (CM) on the probability of conception in New York State Holstein cows. Data were available on 55,372 artificial inseminations (AI) in 23,695 lactations from 14,148 cows in 7 herds. We used generalized linear mixed models to model whether or not a cow conceived after a particular AI. Independent variables included AI number (first, second, third, fourth), parity, season when AI occurred, farm, type of CM (due to gram-positive bacteria, gram-negative bacteria, or other organisms) in the 6 wk before and after an AI, and occurrence of other diseases. Older cows were less likely to conceive. Inseminations occurring in the summer were least likely to be successful. Retained placenta decreased the probability of conception. Conception was also less likely with each successive AI. The probability of conception associated with the first AI was 0.29. The probability of conception decreased to 0.26, 0.25, and 0.24 for the second, third, and fourth AI, respectively. Clinical mastitis occurring any time between 14 d before until 35 d after an AI was associated with a lower probability of conception; the greatest effect was an 80% reduction associated with gram-negative CM occurring in the week after AI. In general, CM due to gram-negative bacteria had a more detrimental effect on probability of conception than did CM caused by gram-positive bacteria or other organisms. Furthermore, CM had more effect on probability of conception immediately around the time of AI. Additional information about CM (i.e., its timing with respect to AI, and whether the causative agent is gram-positive or gram-negative bacteria, or other organisms) is valuable to dairy personnel in determining why some cows are unable to conceive in a timely manner. These findings are also beneficial for the management of mastitic cows (especially those with gram-negative CM) when mastitis occurs close to AI.     

Finite-Element Analysis and Vibration Testing of a Two-Span Masonry Arch Bridge

This paper presents the analytical modeling, modal testing, and finite-element model updating for a two-span masonry arch bridge. An Ottoman masonry arch bridge built in the 19th century and located at Camlihemsin, Rize, Turkey is selected as an example. Analytical modal analysis is performed on the developed 3D finite-element model of the bridge to obtain dynamic characteristics. The ambient vibration tests are conducted under natural excitation such as human walking. The operational modal analysis is carried out using peak picking method in the frequency domain and stochastic subspace identification method in the time domain, and dynamic characteristics (natural frequencies, mode shapes, and damping ratios) are determined experimentally. Finite-element model of the bridge is updated to minimize the differences between analytically and experimentally estimated dynamic characteristics by changing boundary conditions. At the end of the study, maximum differences in the natural frequencies are reduced on average from 18 to 7% and a good agreement is found between analytical and experimental dynamic characteristics after finite-element model updating.     

Mercurial Commitments with Applications to Zero-Knowledge Sets

We introduce a new flavor of commitment schemes, which we call mercurial commitments. Informally, mercurial commitments are standard commitments that have been extended to allow for soft decommitment. Soft decommitments, on the one hand, are not binding but, on the other hand, cannot be in conflict with true decommitments. We then demonstrate that a particular instantiation of mercurial commitments has been implicitly used by Micali, Rabin and Kilian to construct zero-knowledge sets. (A zero-knowledge set scheme allows a Prover to (1) commit to a set S in a way that reveals nothing about S and (2) prove to a Verifier, in zero-knowledge, statements of the form x∈S and x?S.) The rather complicated construction of Micali et al. becomes easy to understand when viewed as a more general construction with mercurial commitments as an underlying building block. By providing mercurial commitments based on various assumptions, we obtain several different new zero-knowledge set constructions.     

A new method for fetal ECG detection

Presented in this work is the theoretical basis of a new method we propose for the analysis of fetal ECG (FECG). This method is intended to detect the fetal HR from a weak FECG signal, and to supply us with an average FECG complex. The FECG signals studied in this work were recorded from the maternal abdominal wall. The core of our method is the computation of a triple parametric transform, using analyzing functions which have a greater correlation with the ECG signal than the correlation of the standard sine and cosine functions used in a Fourier transform. The functions used are trains of square waves characterized by the width of the square wave, their periodicity, and some initial phase value. This method, applied here to a medical problem, can be more generally applied to handle weak quasiperiodic sharp signals of any origin.     

Out-of-plane behavior of dry-stack brick masonry walls

As a result of the combination of the complex behavior of masonry buildings with insufficient material quality and lack in engineering calculations, a large number of damages has been observed in the earthquakes that occurred in recent years. Therefore, a realistic understanding of the behavior of masonry walls and buildings is necessary to construct seismic-resistant structures. Since masonry walls have many variables, performing experiments in which each variable is present at the same time will make it difficult to understand the behavior. For these reasons, considering the out-of-plane failures that are frequently mentioned in recent earthquakes, in this study, variables in dry-stack brick masonry buildings such as the aspect ratio of the wall (2, 1.33, and 1), the presence of the transverse walls (2, 1, and 0), and the openings in the walls (door and/or window) were taken into account separately. Eighteen different wall configurations were designed, and a total of 48 dry-stack walls having U-shape, L-shape, and I-shape in plan were tested by a specially constructed tilting table setup to determine their out-of-plane behavior. From the test results, it was found that lateral load capacity of the U-shaped walls without openings increased as the aspect ratio (L/H) decreased. No change in capacity was observed in L- and I-shaped walls when the aspect ratio was reduced from 2 to 1. Door and/or window openings were found to affect only the L-shaped walls. In addition, it was determined that failure patterns were affected from the aspect ratio and the presence of the openings.     

Migration of Plasticizer between Bonded Propellant Interfaces

Plasticizer migration across bonded propellant interfaces during cure has been shown to have a measurable effect on propellant properties compared to each propellant by itself. This shows that the curing period is significant to the migration phenomenon. The plasticizer migration has been shown to have a direct influence on tensile strength for short aging periods up to the point the plasticizer reaches equilibrium. The tensile data for short aging periods have been shown to follow an empirical equation connecting the physical characteristics of plasticizer migration with increasing propellant tensile strength. The diffusion coefficient has been evaluated on the basis of this relation from a plot of σ versus t^1/2 and was in good agreement with the diffusion coefficient from the plasticizer content data.